Electric circuit interrupter



Juy 23, 193.

ELECTRIC CIRCUQ" 'I' ff; EU i L.'

Filed. May :122:21 2 Sheets-Sheet l /L ...Il

David C. FTW-nce Hls Abtov'neg Inventor:

July 28, 1936. D, C, pRlNCE ELECTRIC CIRCUIT INTERRUPTER 2 Sheets-Sheet2 Filed May 23, 1954 Inventor. David C. F'rhce, bg N Hi Attorv'negPatented July 2s, Vv193.6

PATENT OFFICE 2,049,318 ELECTRIC cmcmr INTERRUPTER David C. Prince,Swarthmore, Pa., assignor to General Electric Company, a corporation ofNew York Application May 23, 1934, Serial No. 727,146

'z claims.

My invention relates to electric circuit interrupters, more particularlyto circuit interrupters of the uid-blast type wherein pressure isutilized to effect a blast of arc-extinguishing or insulatlng liquidthrough a break in the circuit to be interrupted, and has for itsprincipal object the provision of an improved circuit interrupter of theaforesaid type which shall have high interrupting capacity and beeiiicient and positive in operation and simple and compact inconstruction.

In accordance with one aspect of my invention for example, pressure isgenerated within a fixed casing by blowing of a fusible element immersedin an insulating liquid and connected in the circuit to be interrupted,and the aforesaid liquid blast is directed through a break in saidvcircuit for extinguishing arcing at that point.

My invention will be more fully set forth in N the following descriptionreferring to the accompanying drawings, and the features of noveltywhich characterize my invention will be pointed .out with particularlyin the claims annexed to and forming a part of this specification.

u Referring to the drawings, Fig. 1 is a perspective View, partly insection, of a fluid-blast circuit interrupter embodying my invention;Fig. 2 is an elevational view, partly in section of the circuitinterrupter shown in Fig. 1; Fig. 3 is an ele- 30 vational view, partlyin section, of a type of oil immersed fuse illustrating an applicationof my Invention; and Figs. 4, 5, 5a, and 6 are elevational and planviews, partly in section, of forms my invention may assume.

35 The fluid-blast circuit.v interrupter illustrated by Figs. l and2comprises a cylindrical casing I which may be formed of a suitableinsulating material, as a mechanically strong fibrous material, andterminalsZ and 3 which are adapted to o be connected in the circuit tobe interrupted.

The casing I contains an arc-extinguishing or insulating liquid, as oilfor example, and is closed at its upper end and at the lower end as byan insulating ring 4 and plug 5.

45 Connected in series with the terminals 2 and 3 is the fusible elementor link 6 and circuit con-` trolling means, as a second fusible element1, which is adapted to form a break in series with the fusible element6. The fusible links 6 and 5, 1 may be composed of any suitablematerial, as cadmium for example. The fusible element 6 is immersed inthe insulating liquid at the lower part of the casing and is preferablyremotely positioned with respect to the fusible element 1 which 5 ispositioned adjacent and opposite an exhaust (Cl. Zoll-120) liquiddirected transversely through the arc path and exhaust passage 8.

Means for mounting and electrically connecting the fusible elements 6and 1 in the circuit between the terminals 2 and 3 comprise any suit- 15Aable arrangement and as illustrated, by way of example, the/fusibleelement 6 is connected to a pair of conducting members 9 and I0 havinginwardly turned portions 9 and I0 which are spaced and interconnected bythe fusible element 6 by screws, or the like, as clearly illustrated inFigs.V 1 and 2. The conducting member I0 extends along one side of thecasingl I and is connected to a conducting strip II --which is in turndirectly connected to the terminal 3 in a suit- 25 able manner', as byscrews or the like. The casing I is cut away as at I2 so that theplate-like terminal 3 forms a substantially flush insert in the casingwall forming thereby a. direct electrical connection between theexterior of the casing and one terminal of the fusible element 6. Theconducting member 9, which is connected tothe other terminal of thefusible element 6 and which may be suitably secured to the side wall ofthe insulating casing I as by a countersunk screw 9" extending throughsaid wall, extends along the opposite side of the casing I and comprisesthe support for the lower terminal of the fusible element 1. The otheror upper terminal of the fusible element 1 is connected to a con- 40ducting strip I3, which is in turn connected to a conductor I4terminating in the terminal 2 in a manner similar to that abovedescribed.

In case of a replacement the lower plug 5 is readily removable forobtaining access to the fusible element 6 and for replacing the same andthe exhaust passage 8 permits ready access to the fusible element 1 andthe terminals thereof so that the same may be replaced through the wallof the casing, as clearly illustrated by Fig. 2.

The casing I may be entirely or partially filled with insulating liquiddepending on the circuit interrupting requirements of the device. In theinterruption of heavy short circuit currents, con- Siderable pressuremay possibly be generated within the casing and for that reason a smallspace above the liquid level forming a gas cushion may be desirable forrelieving excessive bursting pressures within the casing. For the samereason the dimensions of the exhaust passage 8 may vary in accordancewith the operating requirements of the device.

In operation my improved circuit interrupter not only is effective tointerrupt the normal current rating within one-half cycle of commercialfrequency alternating current, but operates generally with very littleformation of gas and resulting gas pressure within the casing. Thecircuit is consistently cleared with practically no disturbance otherthan an occasional slight report.

Fig. 3 illustrates a form of oil immersed fuse to which my invention maybe readily applied. The casing I housing the circuit interrupterillustrated by Figs. l and 2 is mounted as a unit within a housingcomprising an oil tank I5 and a cover structure |6 having lateraldepending outlets I1 and I8 for the electrical connections, or cables IEl and 20, connected to the device. The cables I3 and 20 are mountedwithin insulating bushings 2| and 22, respectively, which makeliquid-tight joints with the cover structure I6. The aforesaid cableswhich extend within the cover structure are looped over and extendwithin the tank I5 terminating in the terminal structures 23 and 24carried by an insulating shell 25. The insulating supporting shell orstructure 25 is carried by insulators 25 secured to the cover structureI6. The terminal structures 23 and 24 linclude the wire-contact members26 and 21, respectively, which are adapted to engage and coact with theterminals 2 and 3 of the fluid-blast circuit interrupter. The contacts26 and 21, which are sultably connected, as illustrated, to the terminalstructures may be of resilient construction so as to make good contactengagement with the terminals 2 and 3 in normal operation of the devicewhich, as illustrated, is connected directly in the circuit includingthe cables I9 and 20.

The cover structure I6 is provided with a central opening 30 throughwhich the circuit interrupter I may be withdrawn for inspection andreplacement of fuses, etc. To this end the cover structure I 6 isprovided with a cap 3| having a depending structure 32 which isconnected, as at 33, by a through-pin to an extension 34 secured to thecasing I of the circuit interrupter. A fluid tight joint between the cap3| and the cover I5 is formed by a resilient gasket 35, the cap 3|providing likewise a breathing or venting structure communicating withthe interior of the device or passage 36.

In practice, the tank I5 is lled with insulating oil at or above thelevel of the exhaust passage 8 of the circuit interrupter so that aftera circuit -interruption the circuit interrupter may be withdrawn throughthe top of the casing by the cap 3| without disturbing the permanentelectrical connections or necessitating removal of the oil tank I5 byreason of the sliding connections at the terminals 2 and 3. Afterreplacement of the fuses, the circuit interrupter is again lowered intothe tank I5 so that the terminals 2 and 3 are in engagement with thecoacting contacts 26 and 21 and the unit is in readiness for anothercircuit interrupting operation.

There is illustrated by Fig. 4 a circuit interrupter wherein the circuitcontrolling means adapted to form a break in series with the fusibleelement comprises a pair of contacts separable in response to pressuregenerated by blowing of said fusible element. As illustrated, a casing4l containing an insulating liquid 4|, as oil, has mounted therein atits lower end a fusible element 42 connected in series with circuitcontrolling means 43. The casing 40 comprising an insulating cylinder issuitably closed, as by end caps 44 and 45, and provided with arestricted passage 46 adjacent its mid-portion. The fusible element 42is connected to a terminal 42 mounted in the end cap 44 and to astationary conductor stud 41 supported within the casing as byinsulating structure 48. The upper wall of the insulating structure 48is provided with apertures 49.

The circuit controlling means 43 comprises a movable contact member 5I)having a flanged or piston-like portion 5| normally closing the passage46 and the oil-containing chamber formed beneath the same. The contact50 is resiliently biased by a spring 52 into engagement with thestationary stud or contact 41, the contact 5I) being suitably guided, asat 53, through the terminal end cap 45.

In operation, blowing of the fusible element 42l in response to excesscurrent generates pressure within the oil 4I in the lower chamber so asto force the contact 50 away from contact 41 to form the second breakand open the exhaust passage 46. The pressure generated likewise forcesa blast of oil through the passage 46 and through the arc within therestricted passage 46 between the separating contacts so that thecircuit is quickly interrupted. Since the fusible element 42 is alreadyblown, the gap at that point which is effectively insulated by oil issufficient to prevent reestablishment of arcing so that the spring 52may return the contact 50 to its normal contacting position.

In the above-described device the strength of l the arc-extinguishingblast may be regulated to a certain extent by design of the exhaustpassage 46 and the spring 52 in accordance with the interruptingrequirements of the device. The spring 52 of course confines thepressure within the pressure chamber until it builds up to apredetermined and effective blast'value for actuating the movablecontact 50. With this arrangement the contacts 50 and 41 are separatedat the most effective time; that is, during the occurrence of a strongblast of oil from the lower chamber. The arc drawn between theseparating contacts is therefore efllciently and quickly interrupted. Anaperture 40' may be formed in the upper part of the casing for ventinggases.

Fig. 5 illustrates an arrangement generally similar to that shown inFig. 4 except that the oil blast is directed in a transverse cross jetthrough the arc between the separating contacts. In this arrangement themovable contact 50 is connected through a crosshead 50 to a pair ofdepending plungers 5I' which are acted upon by pressure within the lowerchamber. The separation of contacts 50 and 41 takes place within atransverse passage or channel 55 which is formed in an insulating baffle56. The plungers or pistons 5I' for actuating the movable contact extendthrough apertures in the baille 56 at opposite sides of the passage 55,as indicated by Fig. 5a, so that when the fusible element blows during acircuit interrupting operation, pressure within the lower chamber actingon the pistons 5I causes separation of the contacts within thetransverse passage 55 and a blast of oil through said passage across thearc and into the upper chamber. For the purpose of increasing theeffectiveness of the oil blast and for introducing a safety factor when-come and the contacts separate.

high bursting pressures are encountered, there is provided means, as agas cushion, for absorbing and storing energy generated by blowing ofthe fuse link. In the case of a very sudden rise of pressure uponblowing of the fuse link,` the gas cushion not only tends to preventpremature separation of the contacts vbut also fracture of thepressure-confining casing.

The other function above referred to, namely, storing of energy, is tomaintain a high velocity oil blast through the arc at a current zero..An alternating current circuit is normally interrupted at a currentzero at which there is no gas evolution and consequently no source ofpressure. The compressed gas in the gas cushion serves to store energyduring the high current values so that the velocity of the oil throughthe blast passage is maintained at a time when it is most effective,that is, at the current zero.

In the arrangement-illustrated, the entrapped gas cushion 4i formed bythe depending baille portion 56f functions as described above and allowssuiiicient blast pressure to build up within the lower chamber beforethe spring 52 is over- The contacts 50 and 41 when in engagementsubstantially close the transverse passage-55 so that the oil blast isreleased upon separation of the contacts to in terrupt the circuit at acurrent zero.

In Fig. 6 the circuit interrupter comprises an insulating tubular casing60' sealed at its opposite ends by conducting terminal caps l and 62 andcontaining a suitable arc-extinguishing or insulatlng liquid 63 in whichis immersed a fusible elementl.

In the present instance the insulating liquid may be a halogen'atedhydrocarbon such for example as chlorinated benzene or chlorinateddiphenyl which when subjected to the decomposing influence of anelectric are gives oil' chlorine gas as contrasted with the explosivegas` mixture resulting from arc interruption within oil.

The insulating liquid and fusible element are contained within acapsule-like member 65 of conducting material sealed at its vupper end,by an insulating plug 66 through which the `tubular conductor 61extends. The upper end of the tubular member 61 is normally closed andsealed, as by a cap-like member 68, forming a movable contact of thecircuit controlling means/in series with the fusible element 64. 'I'hecontact member 68 is suitably secured, as at 69, to the ltube 61 bysolder or the like. The fusible element 64 is con- 4 nected at one endto a conductinglmember l0 in turn supported by an insulating vbracket1li', a second fuse wire 1l interconnecting the conductor 10 and thecontact member Cl.

For the purpose of providing a gas cushion of the above describedcharacter in the chamber containing the vfusible element, the tube 61extends .within the liquid 63 so as to form an annular space 12providing a gas cushion upon 1nterruption of the circuit. When thefusible element 6l is blown in response toexcess current, pressuregenerated Within the member l5 rapidly builds up until it is suilicientto displace the contact member 6B. When this occurs the blast pressuredirects liquid through the tube Il and through the arc stream. A tensionspring 13 serving, together with the conductor 14. electrically toconnect the contact member il to the terminali is provided to acceleratethe opening of the contact member 68 when it is displaced by the blastpressure. The insulating walls oi' the tube i0 conne the arc drawn atthe break between the contact 6l and the tube 61 substantially withinthe liquid blast from the lowerpart of the casing.

The gas cushion 'l2 functions similar to cushion 4I as described inconnection with Fig. 5 and' prevents premature displacement of thecontact member 68 since a comparatively small displacement of the liquid63 before the pressure is built up sufficiently serves to compress thegas within the space 'l2 rather than displace the contact member 68, Thefusible element 64 is designed to blow slightly ahead of the link -ll sothat adequate blast pressure is generated within the liquid 63. Inpractice the link 1| would probably be broken mechanically by blowingout of the member 68.

The present device is designed so as to be completely sealed andself-contained, there being noV liquid throw or emission of gas duringthe cir- 'cuit interruption. For this purpose the upper part of thecasing 60 is provided with perforated bailles 15 above which a suitablegas absorbing 'material 16, as sodium4 hydroxide in the presentinstance, is disposed. When the liquid 63 is ex-` jan arc-extinguishingliquid, a fusible element immersed and arranged to blow initially insaid liquid within said casing, said casing having an exhaust passageremote with respect to the point of initial blowing of said fusibleelement, circuit controlling means arranged to form a break in serieswith said fusible element normally closing said exhaust passage,pressure generated within said liquid by.blowing of said fusible elementcausing displacement of said circuit controlling means and a blast ofliquid through the aforesaid break, and means confining the arc drawn atsaid break substantially within the liquid,

blast from said casing.

2. Anelectric circuit interrupter of the fluidblast type comprising acasing containing an arcextinguishing liquid, a fusible element immersedand arranged to blow initially in said liquid within said casing, saidcasing having a restricted exhaust passage, circuit controlling means arranged to form a break in series with said fusible element including acontact member secured to said casing and normally sealing said exhaustpassage, said member adapted to be displaced by predetermined pressuregenerated within said liquid by blowing of said fusible element, andmeans confining the arc drawn at said break to a passage through which ablast of liquid from said casing is directed by said pressure.

3. An electric circuit interrupter of the iluidblast type comprising afixed casing containing an arc-extinguishing liquid, means immersed andarranged to generate pressure in said liquid in response to a circuitcondition, said casing having an exhaust passage, and circuitcontrolling means normally closing said exhaust passage and casing, saidcasing forming with respect to said liquid a gas cushion opposingdisplacement of lilil said liquid until a predetermined pressure fordisplacing said circuit controlling means is obtained.

4. An electric circuit interrupter of the fluidblast type comprising acasing containing an insulating liquid, a fusible element immersed insaid liquid, a tubular member forming an exhaust passage for saidcasing, said tubular member at one end extending within said casing andbeneath the liquid level so as to form an annular gas space above saidliquid, circuit controlling means arranged to form a` break in serieswith said fusible element including a contact member normally closingthe opposite .end oi' said tube, and frangible means securing saidContact member to said tubular member, blowing of said fusible elementresulting in displacement of said contact member coincident with a blastof insulating liquid through the aforesaid break.

5. An electric circuit interrupter of the iluidblast type comprising acasing containing an insulating liquid, a fusible element immersed insaid insulating liquid, means providing a restricted exhaust passage forsaid liquid, circuit controlling means arranged to form a break inseries with said fusible element normally closing said exhaust passage,blowing of. said fusible element causing displacement of said circuitcontrolling means coincident with a blast of insulating liquid throughthe aforesaid break, and means disposed in another part of said casingbeyond said exhaust passage for absorbing gases generated within saidliquid during an arc interrupting operation, said casing beingcompletely sealed so as to form a. self-contained circuit interruptingunit.

6. An electric circuit interrupter of the fluidblast type comprising acasing containing an insulating liquid, a fusible element immersed insaid liquid, means forming an exhaust passage for said liquid, circuitcontrolling means arranged to form a break in series with said fusibleelement including a. contact normally disposed in said exhaust passage,and means including a piston member operatively connected to saidcontact and actuated by pressure generated within said insulating liquidby blowing of said fusible element causing opening movement of saidcontact coincident with a blast of insulating liquid arcing at saidbreak.

7. An electric circuit interrupter of the :duidblast type comprising acasing containing an insulating liquid, an insulating baille in saidcasing forming a restricted passage, said baille being immersed in saidliquid and forming a pressure chamber nlled with said liquid, a fusibleelement disposed in said chamber, circuit controlling means arranged toform a break in series with said fusible element including a contactnormally disposed in said exhaust passage, means including a pistonmember operatively connected to said contact, and a spring connected tosaid piston member for opposing pressure generated within said chamberby blowing oi said fusible element, predetermined pressure causingopening movement of said contact coincident with a blast of insulatingliquid through the aioresaid passage for interrupting arcing atsaid/break.

DAVID C. PRINCE.

4through the aforesaid passage for interrupting 15

